The present invention relates to a solid-state imaging device, and more particularly, to a solid-state imaging device of a high-resolution type which is used in broadcasting video cameras and capable of promoting the high integration of elements in photosensitive region.
FIG. I shows an example of a construction of a conventional solid-state imaging device of a high resolution type which is used in broadcasting video cameras. The solid-state imaging device comprises a plurality of pixels 1 which are disposed in rows and columns, respectively, and for storing signal charges which are generated by light reception, vertical CCD (charge coupled device) registers 2 for transferring the signal charges which are generated and stored in the pixels 1, storage registers 3 which are disposed under the vertical CCD registers 2 and temporarily storing the signal charges, a horizontal CCD register 4 which is disposed near an undermost portion of the storage registers 3 and for transferring signal charges of one pixel line, and an output circuit 5 for externally outputting a voltage which is converted from the signal charges transferred from .the horizontal CCD register 4. The solid-state imaging device is called an FIT (frame interline transfer) type which is well known from our prior Japanese application (see Japanese Patent official gazette of Laid-open Publication No. 55-52675-1980-).
Since a solid-state imaging device of the FIT type has the storage registers 3, this type device can increase a transfer speed of the vertical CCD register 2 in comparison with the further conventional solid-state imaging device of a conventional interline type, so that it is possible to have extremely improved smear characteristics. Accordingly, this type of device is used in broadcasting video cameras and certain types of personal use cameras.
In this conventional solid-state imaging device, one unit cell has pixels 1, charge read-out regions 6, vertical CCD register 2, and an element separating region 7, as shown in FIG. 2, and a pitch P.sub.H in the horizontal direction is the sum of widths of the pixel 1, the register 2 and the distances between pixels 1 and register 2. Namely, the pitch P.sub.H is represented by the equation of "P.sub.H =L.sub.1 +L.sub.2 +L.sub.3 +L.sub.4 ".
Furthermore, a pitch P.sub.V in the vertical direction is the sum of the widths W.sub.1 and W.sub.2 of the pixel 1 and the element separating region. That is, the pitch P.sub.V is represented by the equation of "P.sub.V =W.sub.1 +W.sub.2 ".
As understood from the construction shown in FIG. 2, the pitch size in the horizontal direction is substantially the same as the size in the vertical direction in spite of providing the charge read-out region 6 between the pixel 1 and the vertical CCD register 2. Accordingly, it is difficult to integrate the circuit in the horizontal direction, so that the pitch size in the horizontal direction determines the upper limit o the number of the pixels. In accordance with increased pixels in the future, a high integration in the horizontal direction is required by means of the increase of the pixels in the horizontal direction because it is impossible to increase the pixel number in the vertical direction which is determined by the number of the horizontal scanning lines such as 525 lines in an NTSC system, 1125 lines in a high-vision and the like. However, high integration in the horizontal direction is difficult in comparison the high integration in the vertical direction as described above, and becomes a problem in that forcible integration results in the deterioration of the smear characteristics and sensitivity.